Aquatic Ecosystem and Terrestrial Ecosystem!
(i) Aquatic Eco-system:
On the basis of salt content, aquatic eco-system can be divided into fresh water eco-system and marine eco-system.
The fresh water eco-system are usually named according to the size and nature of the aquatic body. Hence, the fresh water eco-system may be pond eco-system, lake eco-system, river eco-system and spring eco-system.
(ii) Terrestrial eco-system:
On the basis of the habitat conditions, the terrestrial eco-system can be divided into four sub-eco-systems.
(a) Grassland eco-system.
(b) Forest eco-system.
(c) Desert eco-system.
(d) Artificial eco-system or man-made eco-system.
Pond as an Eco-System:
Pond is a fresh water aquatic eco-system. It demonstrates lucidly a self-sufficient and self-regulating eco-system.
Basing on the depth of water and types of living organisms, a pond may be divided into three different zones namely:
(ii) limnetic, and
The littoral zone is the shallow water containing rooted plants and this zone of the pond receives maximum light. The limnetic zone ranges from the shallow to the depth of effective light penetration and contains small crustaceans, rotifiers, algae, insects and their larvae. The pro-fundal zone is the deep water part where there is no effective light penetration and it is associated with organism like snails, mussels, crabs and worms.
It has two main components:
(a) Abiotic component, and
(b) Biotic component.
(A) Abiotic Component:
The abiotic component of pond consists of three sub-components:
(i) Physical Components:
The physical components influencing pond eco-system are heat, light and pH value of water.
(ii) Inorganic Components:
The basic inorganic compounds of a pond system are carbon dioxide, water, oxygen, nitrogen, phosphorous, calcium, etc.
(iii) Organic Components:
The chief organic compounds are amino acid, humic acid, fatty acid, carbohydrates, lipid, etc. A smaller fraction of inorganic and organic components remains in insoluble form in water and becomes available for the use of producers as nutrient.
However, the major portion of these remains stored in particulate matter at the bottom sediments as well as in the bodies of the living organisms. The rate of release of abiotic substances depends upon the intensity of solar radiation, cycles of temperature and climatic regimes,
(B) Biotic Component:
The various organisms constituting the biotic component are:
(c) Decomposer or transformer
These are autotrophic green plants and some photo-synthetic bacteria which are capable of preparing organic substances like carbohydrates, proteins, lipids, etc. with the help of solar radiation and minerals from the water and mud.
The producers are of the following types:
These are comparatively larger plants which include partly or completely submerged, floating and emergent hydro-phytes. Some common examples are Trapa, Typha, Eleocharis, Sagitattaria, Nymphaea, Hydrilla, Potamogeton, etc.
These are minute floating or suspended and non-rooted lower plants. These are distributed throughout the ponds as deep as light penetrates. These constitute the autotrophic component of pond and the life of heterotrophic component depends upon it. Some common examples are Volvox, Euglena, Algae, etc.
In a pond eco-system, the primary consumers are the tadpole, larvae of frog, fish and other aquatic animals which consume green plants or algae as their food (herbivorous). These herbivorous aquatic animals become the food of secondary consumers. The examples of secondary consumers are frogs, fishes, snakes, crabs, etc. The secondary consumers become the food of tertiary consumers e.g. large fishes, turtles.
(c) Decomposers and Transformers:
There are a large number of heterotrophic bacteria, flagellates and fungi distributed throughout the pond specially more abundant in the mud. These micro-organisms attack the dead organism (plants and animals) and decompose the complex organic compounds into simple inorganic compounds and elements.
These are also known as micro-consumers because during the process of decomposition, these absorb a fraction of organic compound. The rate of decomposition and transformation depends upon the physical factors like temperature. When the physical factors are favourable for the decomposers and transformers, the rate of decomposition and transformation from complex organic compounds to simpler inorganic compounds becomes faster.
Thus, from the above discussion, it is clear that a pond has all the necessary abiotic and biotic components which interact with each other and bring about the cycling of materials.
Grassland as an Ecosystem:
One of the simplest and self-sufficient terrestrial eco-system is the grassland which occupies approximately 19 per cent of the earth’s surface.
Just like other eco-systems, a grassland ecosystem is composed of different components:
It consists of various nutrients present in soil or in aerial environment. Abiotic substances like carbon dioxide, water, nitrates, phosphates, sulphates, etc. supply the elements like C, H, O, N, S, P, etc. from air and soil. Besides, some trace elements are also present in the soil.
(B) Biotic Component:
The various organisms constituting biotic components can be divided into the following headings:
The grasses and few forbs and shrubs are the autotrophs or producers of a grass-land eco-system. These prepare carbohydrate by the process of photo-synthesis in the presence of light, light trapping pigments (chlorophylls), carbon dioxide of the atmosphere and water from the soil. Some producers, species are Dicahanthiun, Cynodon, Desmodium, Digitaria, etc.
There are mainly three types of consumers:
(i) Primary Consumers:
The primary consumers are herbivorous mainly grazing animals like cows, buffalos, deer’s, goats, sheep’s, etc. In addition to the grazing animals some insects, termites and millipedes feed on the grasses.
(ii) Secondary Consumers:
These are the carnivores feeding on herbivores. Some common examples of secondary consumers are foxes, snakes, frogs, lizards, etc.
(iii) Tertiary Consumers:
These are the carnivore feeding on secondary consumers. Some common examples are snakes, hawks, etc. (c) Decomposers or Transformers: These are the microbes which decompose and transform the organic substances of dead organisms (plants or animals) into inorganic components. The inorganic components are subsequently absorbed by the producers for the preparation of food. The microbes are mainly fungi, some bacteria and actinomycetes.
A forest is a complete functioning ecosystem that supports in numerable plant and animal species as well as land, water and air subsystem. It is a heterogeneous complex of living and nonliving elements which are interrelated. It may be small like a backyard or large like the planet earth which depends on the range of individual species or group of species, geology and other issues.
Different types of forest ecosystems and their characteristics are as follows:
(A) Temperate Forests:
Temperate forests are the regions which have seasonal variation in climate i.e., the climate changes a lot from summer to winter. The annual rain fall is about 750- 2000 mm and soil is rich. Such types of forests are found in western and central Europe, Eastern Asia and eastern North America.
These forests have deciduous trees (oaks, maples etc.) and coniferous trees (pines). These forests contain abundant micro-organ- isms, mammals (hares, deer, fares, coyotesetc). Birds (warblers, wood peckers, owls etc.) snakes, frogs, salamanders etc.
(B) Tropical Rain forests:
Tropical rain forests are special ecosystems which accommodate thousands of species of animals and plants. These untain usually densely packed tall trees those form a ceiling from the sun above. The filing prevents the growth of smaller plants. However, the areas where the sunlight can reach the surface become the place of growth of a number of interesting plants.
The annual rainfall in these regions is about 80 inches. The temperature remains almost same throughout the year. Such types of forests are found in Brazil of South America (Neotropic) and Central and West Africa. The area is always warm and muggy.
Structure of forest ecosystem:
The living organisms existing within the ecosystem interact with each other and with the surroundings. Each organism has a definite role in sustaining the ecosystem. The abiotic components of such ecosystem include physical components (light, heat, etc.), inorganic components (carbon dioxide, water, oxygen, nitrogen, phosphorous, calcium etc.) and organic components (amino acids, humic acid, fatty acids, carbohydrates etc.).
The various organisms constituting the biotic components are:
(iii) Decomposes or transformer.
The trees and other plants produce the basic food stuff (carbohydrate) and energy by the process of photosynthesis which are subsequently un-assumed by other organisms within the food chains and food webs.
All animals including mammals, insects and birds are called consumers. The primary consumers eating only plants are termed as herbivores. Secondary consumers feed on herbivores, are termed as carnivores. Tertiary consumers feed on small carnivores, are also carnivores. Omnivores consume both plant and animals matters.
The materials like leaves, needles, old branches, dead plants and dead animals are decomposed by worms, microbes, fungi, ants and other bugs. The decomposers break these items down in to their smallest primary elements to be used again i.e., the decomposers sustain the nutrient cycle of ecosystem.
Function of forest ecosystem:
Mainly three important cycles are operating within forest ecosystem.
Let us discuss the different cycle existing in forest ecosystem and their functions:
(i) Energy cycle:
The energy from the sun is converted in to biomass by the green plant which is subsequently consumed by other organisms. The biomass is converted in to other forms of energy by consumers and decomposers.
(ii) Water cycle:
Water cycle is operated with in forest ecosystem. The water cycle collects, purifies and distributes world’s water. The processes involved in water cycle are transpiration, evaporation, condensation, precipitation, infiltration etc.
(iii) Nutrient cycle:
Nutrient cycles operating in forest ecosystem regularly transform nutrients from the nonliving environment (air, soil, water, rock) to the living environment and then back again.
A desert is an area where evaporation exceeds precipitation. The annual precipitation in these regions is in between 25 mm and 50 mm, spread unevenly over the year. The desert gets heated during day time and temperature becomes high. The night can be quite cold since the lack of vegetation allows the heat from the ground to radiate away into atmosphere very quickly. The desert soil has very little organic matter but it is rich in minerals.
The desert plants have wax coated leaves, deep and widely spread shallow roots. These try to conserve water by having few or no leaves. The desert animals are usually small in size. They remain under cover during the day time and come out to feed at night. Many animals have thick external shell which reduces moisture loss due to evaporation.
The deserts differ from one another by their soil composition. Some deserts are made of very fine red sands and others consist of sand mixed with pebbles and rocks. The sands are mostly minerals and sometimes oils are found hidden deep within the rocks.
The different components of desert ecosystems are:
(i) Abiotic Component:
The abiotic component includes various nutrients present in the soil and arid environment. Interestingly, the abiotic component is having very little organic matter and water.
(ii) Biotic component:
The various organisms constituting the biotic components are:
The producers capable of producing food by photosynthesis are mainly shrubs or bushes, some grasses and a few trees. Most of the desert plants are succulents and others have seeds that remain dormant until rain awakens them. The desert plants include many species of cacti, desert rose, living rock, welwitchia etc.
The animals consuming the producers are insects, reptiles etc. There are also some rhodents, birds, some mammalian vertebrates.
The desert insects include locust, a special type of destructive grasshopper, Yucca moth, darkling beethe etc. The desert reptiles may be snakes and lizards. The desert birds are sand grouse, gila wood pecker, road runner ostrich etc. The mammals residing in the desert are camels, horses, foxes, jackals etc.
The number of decomposes in the desert are very few because of poor vegetation leading to less organic matter. The usual decomposes are some bacteria and fungi which are thermophillic.